PIIFD [1]} is an improved algorithm based on SIFT [2]} to solve the problem of the full inverse (light and dark flipping) and nonlinear intensity difference in multi-source retinal images. Similar problems are evident in multi-source remote sensing images, which can be seen through the image pairs in Fig. 2 and Fig. 3. So in this paper, the PIIFD algorithm is used to describe the feature points.
